It is desirable to minimize the amount of human labor expended in maintaining and cleaning buildings. The art has therefore developed autonomous robotic devices that can clean or otherwise maintain or treat hard floors, carpeting and similar surfaces without the necessity for a human to be present during the operation of the device.
Such robotic devices typically have a programmable controller for directing the device in a preferred movement pattern. The controller is linked to motors that drive the wheels of the device. Many of these devices also include sensors to detect positions of the device relative to a pre-set path or relative to an obstacle such as a wall or a staircase. Other of these devices include programming to provide for a pre-set navigational path, and sensors to detect the presence of unexpected obstacles in the pre-set path such that the pre-set path may be altered to avoid the obstacles.
For example, U.S. Pat. No. 5,682,313 discloses a floor cleaning robot where ultrasonic transponders are placed in a room to help the cleaning robot move about the room. Another example is U.S. Pat. No. 5,165,064 which discloses a mobile robot where infrared beacons are placed in a room to help the robot move about an area.
U.S. Pat. No. 6,049,745 discloses automatic guided vehicles (factory material movers) wherein radio frequency identification (“RFID”) tags are provided along the path over which the vehicle travels. Each RFID tag is capable of conveying at least one unique radio frequency signal to a remote reader in response to electromagnetic excitation fields emitted by a remote interrogator. The vehicle has a computer and the remote RFID interrogator and reader. The computer is responsive to characteristic area conditions identified by the RFID reader for navigating the vehicle through the area. The RFID tags can thereby provide directions to a destination for the vehicle.
Similarly, U.S. Pat. No. 6,459,966 describes a passenger train that is navigated along a route using RFIDs. A route is provided for a vehicle, which corresponds to RFIDs having a memory storing in advance the RFIDs own location information on the route. An RFID interrogator is mounted on the train which transmits radio waves to the RFIDs. In response, the RFIDs provide information to the train's reader regarding location. A controller on the vehicle then controls a moving direction of the vehicle based on the position information to guide the vehicle along the route.
For various other navigational and obstacle avoidance systems applied to robotic devices see generally U.S. Pat. Nos. 6,370,452, 6,594,844, 6,671,592 and 6,690,134.
While various electromagnetic systems have therefore been used for navigational control and obstacle avoidance in autonomous robots, the above listed systems have not been designed to automatically alter the dwell time of the robot in response to temporary conditions (e.g. a heavily soiled area requiring extra cleaning time; a particular area that is so clean as not to require substantial additional cleaning during this cleaning opportunity). As a result, cleaning performance of such robots has not yet been optimized.
Therefore, a need exists for improved robotic floor treaters where the dwell time of the device can be easily and reliably altered to account for temporary conditions.